The invention relates to a plug connector for establishing an electrical contact between first and second conducting track carriers, in particular between a flexible conductor foil and a circuit board.
Originally, conventional plug connectors have been employed for connecting the conducting tracks of two circuit boards with each other. A plug part was attached to one of the circuit boards and a socket part was attached to the other circuit board. By inserting the plug contacts of plug part and socket part into each other, the conducting tracks of the two circuit boards could be connected with each other.
A further development of these plug connectors is to insert one of the circuit boards directly into a socket part of the plug connector, so that contacts provided in the socket part directly make contact with the conducting tracks of the inserted circuit board. One example of such a plug connector is to be found in DE 40 18 947 A1. In the device shown therein, the circuit board to be inserted is provided with an actuation element that has the shape of two noses protruding on both sides of the circuit board to be inserted. During a first phase of insertion, the circuit board can be inserted into the socket part virtually with zero insertion force, since the contacts of the socket part are held at a distance from the circuit board. In a second phase, the noses provided on the circuit board engage the contacts in the socket part, so that the contacts are forced against the circuit board and the final contact force is made available.
A further plug connector is known from DE 199 44 493 A1. It serves in particular for connecting a conductor foil. For making contact with the conducting tracks of the conductor foil, there are provided clip-like contacts in the socket part, the two ends of which resiliently rest against each other. Provided on one of these ends is an actuation arm which cooperates with an actuation protrusion on the plug part carrying the conductor foil. When the plug part is inserted, the clip-like contact is opened during a first insertion phase by acting on the actuation arm, so that the conductor foil can be pushed into the contact. In a second phase, the actuation arm is released again, so that the contact closes and the two ends of the clip-like contact rest on the upper and lower sides of the conductor foil.
It is a disadvantage of these known plug connectors that during insertion of the circuit board or the conductor foil a relative motion inevitably occurs between conducting track or conductor foil on the one hand, and the conducting tracks of conductor foil and circuit board on the other hand, which is necessary for compensating tolerances of the components. This relative motion results in high stress on the conducting tracks, in particular if they are designed so as to be very filigree, as well as in a xe2x80x9cdeadxe2x80x9d conducting track section, i.e. that part of the conducting track which lies behind the contact point and has detrimental effects with high signal transmission speed. A further disadvantage, both in terms of the constructional expenditure and the quality of signal transmission, is the fact that contacts are required which engage the conducting tracks of circuit board and conductor foil, respectively, and which are connected with the conducting tracks of the other conductor foil and circuit board, respectively.
Thus, it is the object of the invention to provide a plug connector in which the conducting tracks, during inserting and contacting, are able to be joined not by a relative motion, but in the nature of a precise spot-landing.
According to the invention, a plug connector for establishing an electrical contact between first and second conducting track carriers, in particular between a flexible conductor foil and a circuit board, comprises a plug part that has a plug housing provided with a cam surface. The first conducting track carrier is shiftably mounted to the plug housing such that it can be shifted, parallel to a plug-in direction of the plug part, starting from an advanced initial position into a retracted contact position. The plug connector further comprises a socket part that includes a socket housing, a pressure application spring and the second conducting track carrier which is received in the socket housing. The pressure application spring has two ends, one end of which forms a supported end received in the socket housing and the other end forms a pressing end that cooperates with the first conducting track carrier if the latter is in the contact position. The pressing end of the pressure application spring is set under tension by the cam surface during inserting the plug part into the socket part and is released not until the plug part is inserted in the socket part to such an extent that the first conducting track carrier has reached its contact position. The most essential aspect of such plug connector is that the conducting track carrier, e.g. a flexible conductor foil or a circuit board housed in the plug part, remains stationary after it has reached its optimum contact position with respect to the conducting track carrier received in the socket housing, while the plug part can be pushed further into the socket part. This motion of the plug part relative to the socket part, with the conducting track carrier of the plug part being stationary at the same time, is used for actuating the pressure application spring which acts on the stationary conducting track carrier of the plug part when it is released again, and forces the conducting track carrier against the opposite conducting track carrier in the socket part. In other words, the movable attachment of the conducting track carrier in the socket part makes it possible to timely separate the two processes of inserting the conducting track carrier into the socket part, on the one hand, and actuating the pressure application spring, on the other, such that the pressure application spring is released not until the conducting track carrier has reached its contact position and a further motion relative to the opposite conducting track carrier of the socket part is not possible any more. It is in this way that the conducting tracks of the two conducting track carriers are not joined by a mutual relative motion, but are forced against each other in the nature of a precise spot-landing only when they have assumed their desired position relative to each other and if possible tolerances during insertion have been compensated already. Since the conducting tracks directly rest on each other, intermediate contact elements are not required either.
According to the preferred embodiment of the invention it is provided for that the first conducting track carrier is a molded plastics circuit board which is arranged on a carriage and that a sliding guide is provided by means of which the carriage is shiftably attached to the plug housing. Further, it is preferably provided for that the second conducting track carrier is a flexible conductor foil. In the case of a molded plastics circuit board, very filigree conducting tracks can be configured at a comparably low expenditure, which what is more may also be provided with raised contact points at their ends. These contact points are particularly of advantage for contacting the conducting tracks of a flexible conductor foil.
It is preferably provided for that the carriage is arranged on the plug housing so as to be also shiftable in a direction perpendicular to the plug-in direction. This may be achieved in that the sliding guide releases the carriage, as soon as the latter has reached the contact position, in a manner such that it can be lifted by the pressing end of the pressure application spring in a direction perpendicular to the plug-in direction and towards the second conducting track carrier. With this design, the sliding guide makes it possible for the carriage to bring about the two relative motions between the conducting track carriers to be contacted, which motions are required for establishing the contact, namely additionally to the shifting motion parallel to the plug-in direction also a shifting motion perpendicularly thereto in order to press the two conducting track carriers against each other. With this, the supported end of the pressure application spring can be firmly held on the socket housing, which simplifies construction.
According to the preferred embodiment of the invention it is provided for that the circuit board of the plug part is connected with a second conductor foil, the second conductor foil extending as far as to a solder surface on the end of the plug housing facing away from the carriage, so that the second conductor foil can be connected there with conducting tracks of a plug card to which the plug part is attached. Using a flexible conductor foil results in the advantage that the conducting tracks of the plastics circuit board can be contacted without impairing the movability of the plastics circuit board attached to the shiftable carrier. The conducting tracks of the plastics circuit board and of the flexible conductor foil can easily be connected with each other by means of bonding wires.
Preferably it is provided for that the solder surface extends on the plug housing at an angle of approximately 20xc2x0 relative to the plane of the plug card. As the conductor foil extends obliquely away from the soldering spot, there will be produced a clearance which allows a visual check of the soldered connection obtained.
Preferably it is provided for that plug contacts are arranged on the plug housing, which are capable of cooperating with complementary plug contacts in the socket housing. It is in this way that additional signals are able to be transmitted. The plug contacts may also serve for power transmission, so that together with the transmission path between the two conducting track carriers there will be obtained a very high level of integration in the plug connector.